The dizzy is probably a reluctor type and may have an internal or external ignitor.
The "RG" dizzy is the reluctor guts of a FWD RB Gemini fitted to a T-series or G-Z engined (RWD) Gemini dizzy, viz:
The RG dizzy above can be modified to suit ANY Isuzu G-series engine (G-Z, G-S, G-U, G-W).
Note that the "RG" includes the ignitor on the lower right side.
But the ignitor can be mounted externally as with the Piazza 4ZC1-t and other 4Z engines prior to the 4ZD engine (which has its ignitor mounted internally like the RB dizzy).
With external ignitor, the G-series dizzy looks like:
The 4ZC1-t Piazza dizzy is similar except it is a mirror image because the 4Z dizzy rotates in the opposite direction to G-series engines.
Before I continue, is your dizzy similar to the above?
And does it have an ignitor, or some "box" in association with the pickup
as show in the lower picture?
The sensor without its cover looks similar to:
IZU069 - ISUZU means a lot to me.